The invention relates to an axial setting device in a housing, especially for actuating a multi-plate coupling whose friction plates are alternately connected in a rotationally fast and axially displaceable way to the one and the other respectively of two parts rotatable relative to one another, which rest against an axially fixed supporting disc and which can be loaded in one embodiment by an axially displaceable pressure disc, comprising a setting disc which is rotatably supported in the housing, which is mounted so as to be axially supported in the housing, which is mounted so as to be axially fixed in the housing and which is rotatingly drivable, a pressure disc which is held in the housing, which is held in a rotationally fast way by anti-rotation means arranged in the housing and which is axially displaceable in the housing, or which can be loadedxe2x80x94in another embodimentxe2x80x94by an axially displaceable setting disc, comprising a setting disc which is rotatably supported in the housing, which is mounted so as to be axially displaceable in the housing and which is rotatingly drivable, a pressure disc which is held in the housing, which is held in a rotationally fast way by anti-rotation means arranged in the housing and which is axially fixed in the housing, ball groove configurations in the surfaces of the setting disc and of the pressure disc, which surfaces face one another, which ball groove configurations extends in the circumferential direction, have oppositely directed gradients and are associated with one another in pairs, so as to jointly accommodate a ball and rotary driving means for the setting disc mounted in the housing.
Setting devices of said type combined with the above-mentioned multi-plate coupling are known in different designs and for different applications.
DE 38 15 225 C2 describes such a device which is integrated into a bevel gear differential drive. The setting disc is directly driven by a conical pinion which engages a bevel gear toothing at the setting disc.
From DE 40 07 506 C1, there is known a device of said type which is used in a manual gearbox. The driving means for the setting disc comprise the same parts as mentioned above, but in addition, they comprise a spur gear reduction drive.
DE 41 06 503 C1 refers to a further development of the latter application. It shows the anti-rotation means for the pressure disc which consist of a tongue-and-groove assembly, with the tongue being connected to the fixed part of the housing and the groove constituting an individual notch at the pressure disc.
EP 0 368 140 B1 describes different applications for setting devices of said type, and inter alia, it can be seen that at its circumference, the setting disc can comprise a worm toothing or helical toothing and setting can be effected by means of a worm driven by a motor and positioned on the motor shaft.
In the case of the devises mentioned first, the driving motor for the setting disc has to be kept under voltage for as long as a positive setting force is to be maintained. This means that the capacity of the motor has to be higher or that the motor requires an additional braking device. The latter device can only be equipped with non-self-inhibiting rotary drive means because the device has to feature as little friction as possible. Irrespective of the latter, in the case of failure involving a voltage brake-down, a reverse motion of the device effected by returning forces is almost impossible due to the high friction in the rotary drive means provided in the form of a worm drive. In a case of failure involving voltage brake-down, a multi-plate coupling closed by rotating the setting disc relative to the pressure disc would be released by the rotary drive means only hesitatingly.
It is the object of the present invention to improve a device of the latter type in that a rapid return from an assumed set position of the device can be effected by simple means in the sense of reducing the setting path. The objective is achieved in that anti-rotation means are designed so as to be releasable from the pressure disc.
The conventional mode of operation is such that, normally, the setting path of the axial setting device is increased or reduced by actuating the rotary drive means which act on the rotatingly drivable setting disc which, via the balls, acts on/is supported on the pressure disc held in a rotationally fast way, with the oppositely directed gradients determining the setting path as a result of the relative rotation of the setting disc relative to the pressure disc. In addition, the special mode of operation in accordance with the invention consists in that, in the case of failure or for special operating conditions, a rapid reduction of the setting path is effected independently of an actuation of the rotary drive means in that the pressure disc is released for rotation purposes so that the counter forces acting on the pressure disc/setting disc act as returning forces which are reduced because the pressure disc is able to rotate freely relative to the setting disc which is held by the rotary drive means in a rotationally fast way or is driven only slowly thereby, with the direction of rotation being determined so as to be opposite to the direction of the oppositely directed gradients of the ball groove configurations. As a result, the setting path of the setting device is very quickly revered automatically.
Releasing the anti-rotation means can constitute a safety measure and can be effected in a case of failure, for instance when there occurs a voltage brake-down. However, it is also possible to provide embodiments wherein the anti-rotation means can be released from the pressure disc for certain operating conditions and can, optionally, also be controlled positively.
In a preferred embodiment, the anti-rotation means can be designed in such a way that they comprise an axially displaceable pin which is aligned relative to the pressure disc, which, in a first position, can engage notches in the circumference of the pressure disc and which, in a second position, is able to move radially out of the notches. The pin must be able to slide in the notches in the direction of displacement of the pressure disc. In particular, the anti-rotation means can comprise an electromagnet which acts on the pin in its holding position, and said holding position can be spring-supported. According to a particularly advantageous embodiment it is proposed that, at the circumference of the pressure disc, the free end of the pin and the flanks of the notches form angles with the radial line which are greater than the self-inhibition angle, so that if the electromagnet is de-energised, with returning forces acting on the pressure disc/setting disc, the pin is suppressed automatically out of his position of engagement in one of the notches. To generate such returning forces, it is proposed in particular that a pretension pressure spring, especially a plate spring, axially acts on the pressure disc towards the setting disc/on the setting disc towards the pressure disc.
It is possible for the anti-rotation means to have any other design; in particular, the form-fitting engagement can be replaced by a friction-locking engagement, i.e. it is possible to provide any type of braking device. In addition, the anti-rotation means, instead of being set electromagnetically, can also be set hydraulically, pneumatically or in any other way.
As far as the design of the rotary drive means are concerned, it is proposed according to a preferred embodiment that, at the outer circumference of the setting disc, there is provided a worm toothing or helical toothing and that there is provided a setting motor on whose shaft, there is positioned a worm which engages the worm toothing or helical toothing. In particular, it is proposed that the worm drive consisting of the setting disc and the worm is self-inhibiting.
Because of the large transmission ratios of worm drives, the driving forces to be proved by the setting motor are low. There is no need for a reduction gear. To be able to stop the setting disc while it is in a rotating position when the setting motor is de-energized, the worm gear is designed so as to be self-inhibiting.
In another embodiment there is provided that at the outer circumference of the setting disc there is provided spur gear toothing and there is provided a setting motor on which shaft there is positioned a spur gear pinion.
A return motion of the setting device as a result of returning forces acting on the pressure disc/setting disc cannot take place. Nevertheless, each position as set can be released without delay by disconnecting the anti-rotation means from the pressure disc. The ball groove configurations between the setting disc and the pressure disc cause the pressure disc to be turned back in the sense of the pressure disc approaching the setting disc/the setting disc approaching the pressure disc.
There is thus provided a setting device wherein, due to a high transmission ratio in the worm device, the setting process can be effected by low driving forces, and because of the self-inhibiting nature of the worm drive, a set rotational position of the setting disc can be maintained permanently when the setting motor is de-energised. Finally, the pressure disc is able to return freely from any positive position as set, in spite of the setting disc being in a fixed position.
It is also possible to use other drive concepts for the rotary drive of the setting disc, such as crown gear drives, spur gear drives, chain drives, belt drives, cog belt drives, etc. In an embodiment, wherein he setting device is driven by a spur gear drive, the driven setting disc is able to return freely by axial motion in the gears ins spite of the setting disc being held rotationally fixed by the drive.